Andrew vonNagy

Author Archives: Andrew vonNagy

Wi-Fi Capacity Infographic

Learn tips and tricks for building a high-performance WLAN!

I teamed up with the great staff at Ekahau to put together this infographic about how to design and deploy high capacity Wi-Fi. It's the second poster in the series, following the Wi-Fi Design Poster that focused on radio frequency (RF) factors.

The Wi-Fi Capacity Infographic covers:

  • An overview of airtime and why it is important
  • Understanding the two primary factors affecting airtime:
    1. Airtime within a cell
    2. Airtime across cells
  • Methods to maximize airtime efficiency to get the most out of your WLAN
  • Channel inventory as it relates to capacity
  • How client capabilities affect airtime consumption, and hence capacity, in a WLAN
  • Factors to consider when selecting infrastructure to deploy
  • Factors to consider with infrastructure placement and configuration
  • Features available within Ekahau Site Survey to set you up for success

Download the Wi-Fi Capacity Infographic today!

High capacity-magnifying glass-landing page image.png

WPA2 KRACK Vulnerability, Getting Information

*** This page is being updated regularly. Please check back periodically. ***

I'm sure everyone who does anything with networking or Wi-Fi has heard about the announced WPA2 KRACK vulnerability. I won't go into depth with my opinion on it. I'd just like to start a collection of useful information in one single place.

First, the security researcher's website on the attack details:
https://www.krackattacks.com/

Second, read these articles and watch these videos by experts:
Mojo Networks / Pentester Academy Videos: http://blog.mojonetworks.com/wpa2-vulnerability
Aruba Blog: http://community.arubanetworks.com/t5/Technology-Blog/WPA2-Key-Reinstallation-Attacks/ba-p/310045
Aruba FAQ: http://www.arubanetworks.com/assets/alert/ARUBA-PSA-2017-007_FAQ_Rev-1.pdf

*IMPORTANT UPDATE*
What's the TL;DR? There are 9 vulnerabilities that are client related and 1 that is AP / Infrastructure related. All are implementation issues, meaning software patching can fix them! Of the 9 CVE's related to clients, ALL can be mitigated with AP / Infrastructure updates as a workaround, but the infrastructure won't be able to determine if failure is from packet loss issues or attack. The long-term fix is definitely client software patching. The 1 CVE related to AP / Infrastructure is related to 802.11r Fast Transition - if you have it enabled you should patch ASAP. If not, no big Continue reading

Capacity Planner Version 2.0 Released

Modern Wi-Fi networks are complex beasts. Despite all the fancy new features in products, the technology is only becoming more complex and the demands on the network are only growing. Wi-Fi is the most heavily used method to transport user data today, eclipsing cellular and LAN traffic volumes according to multiple reports from analysis firms including Cisco, Ofcom, Mobidia, Ovum, and others. Meanwhile, the technical complexity contained within the IEEE 802.11 standard results in a technical document that is over 3,200 pages long!  This means deploying a network right is no easy task.

One of the most difficult aspects to get right when deploying a Wi-Fi network is understanding capacity requirements. It is not sufficient enough to use rule-of-thumb guidelines based on number of clients per access point or number of access points per square foot/meter since they often result in networks that do not adequately meet actual end-user demands and perform poorly. More rigor is required while maintaining simplicity of use so that most network administrators can be confident of a successful outcome.

Essential to wireless network performance and capacity planning is understanding the interaction between access point capabilities, network configuration, client device capabilities, and the RF Continue reading

TDWR 5 GHz Weather Radar Locations and Frequencies

Is your Wi-Fi network close to TDWR weather radar that may impact your deployment?

 

Use this list to know: 

Source: Cisco and WISPA

 http://www.wispa.org/Resources/Industry-Resources/TDWR-Resources/TDWR-Locations-and-Frequencies

 http://www.cisco.com/c/en/us/products/collateral/routers/3200-series-rugged-integrated-services-routers-isr/data_sheet_c78-647116.html

PDF version: 

 http://www.cisco.com/c/en/us/products/collateral/routers/3200-series-rugged-integrated-services-routers-isr/data_sheet_c78-647116.pdf

IMG_3879.PNG

Download the New ‘Wi-Fi Design Poster’ Today!

Performing a proper Wi-Fi design is critical to success. Modern WLANs have grown ever more complex, having to provide high quality coverage, meet density and capacity requirements, facilitate user mobility and roaming, all while minimizing both Wi-Fi interference and external RF interference. The new 'Wi-Fi Design Poster' can provide a quick reference for wireless engineers. The poster was a collaborative effort between myself and Ekahau.

The poster covers the 4 critical aspects of Wi-Fi design, an overview of the design process, and 10 high-performance Wi-Fi tips and tricks.

Download and print yours today! It is available as both a poster and an infographic. We hope you like it :) Please share it if you think others would benefit as well.

Ekahau and Revolution Wi-Fi Design Infographic (vertical).png

Maturing End-to-End Wi-Fi Service Monitoring

Aruba Networks introduced Clarity Live and Clarity Synthetic during their Atmosphere 2016 conference in March. These solutions usher in the beginning of end-to-end Wi-Fi service monitoring by both the infrastructure and client agents to provide Wi-Fi administrators with greater network visibility, proactive monitoring, and synthetic testing in order to minimize Wi-Fi service disruptions. Knowing is half the battle, and quickly narrowing scope and diagnosing problems is one problem the industry has faced since inception. 

Read the entire blog post on the Aruba Airheads Technology Blog.

SSID Overhead, Now There’s an App for that!

One of the more popular reasons that people visit my website is to understand why too many SSIDs is an issue on a WLAN. I've written about performance degradation issues due to network overhead and subsequently released an SSID Overhead Calculator. The drawback to the tool is that it's in Microsoft Excel format. This makes it's use limited to people who have Excel and is only really available on workstations (not mobile devices) which makes it hard to use on-the-fly while in the field or in front of a customer.

Thanks to collaboration with Ryan Adzima, we are announcing the availability of the Revolution Wi-Fi SSID Overhead Calculator as an Apple iOS application today! You can download it here:
https://itunes.apple.com/us/app/apple-store/id1041231876?pt=615227&ct=Revolution%20Wi-Fi&mt=8

The iOS application provides the full functionality of the original tool right on your phone and tablet. You can adjust beacon data rate, beacon frame size, beacon interval, number of SSIDs, and number of APs on the channel. The circular bar displays the amount of overhead that the combinations will cause on your WLAN as well as a severity indication and recommendations to improve performance.

Here are a few screenshots:

SSID Overhead 3.png
SSID Overhead 2.png
SSID Overhead 1.png

Big shoutout to Ryan for working Continue reading

WLAN Triage with the Fluke AirCheck

Disclosure - I was provided an evaluation unit by Fluke Networks to review. However, all opinions expressed in this post are solely my own and in no way constitute a paid arrangement.

The Fluke Networks AirCheck Wi-Fi Tester has been around for a while now. And I'm late to the game, despite having seen its initial release as part of Wireless Field Day 1. I was impressed with the brief hands-on time that I had with the unit back in 2012 as part of that event, but I never had the opportunity to acquire one as part of my job.

I decided to revisit the AirCheck after observing some positive discussion of the unit on Twitter, watching Devin Akin's Fluke webinar, and realizing that its functionality appeared to align with my philosophy that airtime utilization is a key WLAN metric. I've only had a brief time hands-on with the AirCheck, but I'd like to highlight a few of my initial findings.

First and foremost, I view the AirCheck as primarily a tool for WLAN triage. When first stepping on-site to work with an existing WLAN that's experiencing problems, the AirCheck is a great tool to obtain an initial assessment of the environment. It Continue reading

Survey – WLAN Vendor Selection Criteria

Back in 2011, I ran a short 1-question survey, asking readers to rate the importance of various factors when selecting a wireless LAN vendor. The results from that survey are located here:
http://www.revolutionwifi.net/revolutionwifi/2011/06/wlan-vendor-selection-criteria-what.html

The discussion of "what matters most in WLAN success" came up again recently during a conversation I had with Lee Badman on twitter.

I thought it would be a good idea to run the survey again. Please take a moment to anonymously answer this short 1-question survey. The survey will close at 11:45pm CDT (GMT -5:00) on July 31st, 2015.

Create your own user feedback survey

Cheers,
Andrew von Nagy

Push It To The Limit! Understand Wi-Fi’s Breaking Point to Design Better WLANs

This is the fourth and final blog post in the WLAN capacity planning series. Be sure to read the first, second, and third posts.

We all want high performing WLANs. In order to do that we must push Wi-Fi to its limits! 

(Cue Scarface Theme, verse 1)…

“Push it to the limit!
Walk along the perimeter edge
But don’t look up, just keep your head
And you’ll be finished

Survey to the limit!
Past the point of no bandwidth
You’ve reached the edge but still you gotta learn
How to build it

Hit the floor and double your pace
Laptop wide open like an engineer outta hell
And you crush the speed test

Going for the back of every room
Nothing gonna stop you
There’s no wall that strong
So close now, battery near the brink
So, push it!”

We walk a fine line when designing wireless networks, attempting to push as many users and bandwidth through our APs as possible, ensuring adequate capacity is available to meet demand, while not overbuilding the network. But what are the limits and how do we know we’ve hit them? Or more importantly, how do we plan Continue reading

PHY Basics: How OFDM Subcarriers Work

Have you ever wondered just "how" OFDM subcarriers are able to be spaced so tightly together without any guard band in-between? Most Wi-Fi textbooks will simply state that the spacing of the subcarriers allows the harmonics to overlap, thus canceling out any interference.

OFDM subcarrier spacing creates "nulls" canceling out inter-carrier interference (ICI) without the need for guard bands or expensive bandpass filters

OFDM subcarrier spacing creates "nulls" canceling out inter-carrier interference (ICI) without the need for guard bands or expensive bandpass filters

OFDM divides a given channel into many narrower subcarriers. The spacing is such that the subcarriers are orthogonal, so they won’t interfere with one another despite the lack of guard bands between them. This comes about by having the subcarrier spacing equal to the reciprocal of symbol time. All subcarriers have a complete number of sine wave cycles that upon demodulation will sum to zero. 

This tells us that the spacing of the subcarriers is directly related to the useful symbol time (more specifically, the amount of time the transmitter spends performing IFFT). Because of this relationship, the resulting sinc frequency response curves from each subcarrier create signal nulls in the adjacent subcarrier frequencies thus preventing inter-carrier interference (ICI). OFDM is a form of frequency division multiplexing (FDD), which typically requires guard bands between carriers and specialized hardware Continue reading

Wi-Fi Design and Capacity Planning Webinars, May 19th and 21st

Please consider attending webinars I'll be hosting on Wi-Fi design and capacity planning next week with Aruba Networks. I'll be talking about the key aspects to WLAN performance and the approach that I take to integrating coverage and capacity into a holistic design, as well as tools you can use to monitor WLAN performance after deployment to maintain a high-performing network and plan for growth.

These won't be traditional marketing webinars. If you're like me, you get invited to (and avoid) many webinars because they are too sales oriented and lack relevant engineering content. This isn't that. The goal of these webinars is to provide practical, real-world concepts and methods to help you design better Wi-Fi networks. Everyone deserves better Wi-Fi, right?

Register here:

U.S. Webinar - May 19th at 11am PDT / 2pm EDT

EMEA Webinar - May 21st at 15:00 GMT

The 2.4 GHz Spectrum Congestion Problem and AP Form-Factors

2.4 GHz is a junk band...
2.4 GHz is interference ridden...
2.4 GHz is dead...

You've heard all of these dire warnings about microwaves, bluetooth accessories, cordless phones, baby monitors, lions and tigers and bears (oh my!), which will wreak havoc on your WLAN.

Well, I'm here to tell you that 2.4 GHz issues are self-inflicted. Any by self-inflicted I mean that Wi-Fi is the root cause of your Wi-Fi not working well. And specifically your own Wi-Fi. Poorly designed networks with too many APs blasting out too many signals all stomping on one another.

I'm a stickler for proper design, and is a mantra that I've probably beaten to death by this point. One aspect of proper design is deploying the proper number of radios to meet capacity needs. It's something that I talk about in my presentations on this subject and tweet about as well. Too many radios actually degrades performance due to the negative effects of co-channel interference and airtime utilization on a shared channel. More is decidedly NOT better!

“Most WLAN designs today require a significant amount of
2.4 GHz radios to be disabled.”

Most WLAN designs today require Continue reading

Understanding 802.11 Medium Contention

In this post, I dive deep into 802.11 medium contention to understand how it works as a precursor to the final blog post in this series where I’ll detail the two main sources of medium contention, identify Wi-Fi's breaking point (that'll be fun, stay tuned) and how this affects proper WLAN design in order to optimize wireless networks to prevent medium contention from killing your WLAN performance.

Read the full blog post over on the Aruba Networks Tech Blog...

 

This is the third blog post in a series about WLAN capacity planning. Be sure to read the first and second posts.

Cheers,
Andrew

WLAN Capacity Planning: From Concept to Practice [Video]

Last week I presented at the Wireless LAN Professionals Conference (#WLPC) in Dallas, TX. The topic of my presentation was putting the concepts of WLAN capacity planning into practice.

Agenda:

  1. Factors of Network Performance (and why variable contention delay is critical to WLANs)
  2. Iterative WLAN Design Methodology
  3. Hands-On with the Revolution Wi-Fi Capacity Planner
  4. Real-World Example and Walkthrough (including tying capacity planning to RF planning)

The video is now available online:

 

If you would like a review of capacity planning concepts prior to watching the hands-on example, my presentation from last year's WLPC 2014 is also available online.


Cheers,
Andrew von Nagy

Finding Older Articles While The Blog is Migrated

If you hadn't noticed, the Revolution Wi-Fi website was recently migrated from Blogger to Squarespace. While I like the new look on the website, some of the features on the old site aren't yet replicated on the new site. Additionally, cached web search results still point to old URLs causing "webpage not found" errors from Google and others.

If you're looking for older blog posts or pages, you have two options:

  1. Go to the old website still at http://www.revolutionwifi.blogspot.com
    OR
  2. Add the "/revolutionwifi/" directory into URL address for any blog post
    Example:
    http://revolutionwifi.net/2013/05/apple-ios-fast-roaming-with-aerohive-wi.html
    Becomes:
    http://revolutionwifi.net/revolutionwifi/2013/05/apple-ios-fast-roaming-with-aerohive-wi.html

Additionally, all of the categorized article topics are available on the old website at http://revolutionwifi.net/revolutionwifi/p/article-archives-by-topic.html

Finally, I've fixed all of the old URL links embedded within blog posts that were broken right after the blog migration due to the different directory structure. Ugh! But I've fixed this now... so all good there :)

I will also be adding Search and Categories to the new website once I have time. Thanks for your patience while I complete this work!

Cheers,
Andrew von Nagy

Contention Delay Killed the WLAN Star

The Wi-Fi industry seems dominated by discussions on the ever-increasing bandwidth capabilities and peak speeds brought with the latest product offerings based on 802.11ac. But while industry marketing touts Gigabit capable peak speeds, the underlying factors affecting WLAN performance have changed little.

Medium contention is the true driver in the success or failure of a WLAN and we must effectively understand its effect on WLAN performance in order to design and optimize our networks.

Read the full blog article over on the Aruba Airheads Technology Blog...

Multi-Gigabit AP Backhaul – Do you need it?

I was recently asked by a Wi-Fi engineer about the potential need for multi-gigabit backhaul needs from an AP with the pending release of 802.11ac Wave 2. This seems to be a point of confusion for many in the wireless industry. Here's what I told them:

Industry claims of throughput capabilities exceed 1 Gbps are correct from a theoretical standpoint. However, real world client mixes on almost every WLAN will mean that backhaul never approaches even close to 1 Gbps of throughput.

First, when you combine clients of varying capabilities there is no chance of exceeding 1 Gbps backhaul. The only time you will need more than 1 Gbps of backhaul is in POC bakeoffs between vendors, lab tests, and very low-density locations where you have only a few users on an AP radio but they are using top of the line high-end wireless laptops and applications that can push large amounts of data (I'm thinking CAD users here for instance who collaborate and push files of several GBs across the network and want it done fast). This is somewhat counter-intuitive because most people would think off-hand that high-density areas is where you'll need the greater backhaul. But in high-density areas Continue reading

Great Wi-Fi Starts with Proper Design

I’m sure that we have all experienced poorly designed Wi-Fi networks. When a technology is so ubiquitous, so easily accessible, and is increasingly the most relied upon method of Internet access for mobile devices and cloud computing, then there are bound to be some issues. Unfortunately, the prevalence of underperforming Wi-Fi networks is still much too common for my liking.

Great Wi-Fi starts with proper design. There are various approaches to WLAN design that have evolved over time, ranging from providing basic coverage to maximum capacity and situations in-between. 

At one end of the spectrum, we have a basic coverage oriented design. This was the historical way of designing a WLAN that simply involved ensuring adequate signal strength from access points was present in desired locations. At the other end of the spectrum is a design focusing on maximum capacity. This involves careful RF planning in order to integrate the most Wi-Fi cells as possible into a physical area. 

The problem with both of these approaches is that they are the extremes and aren't applicable for many wireless networks. Basic coverage designs may still work for warehouses and some retailers and maximum capacity designs are great for stadiums and Continue reading